/ Experiment-HEP arXiv:0704.3133


Transverse Polarization of Lambda and anti-Lambda Hyperons in Quasireal Photoproduction


Airapetian, A. ; Akopov, N. ; Akopov, Z. ; Amarian, M. ; Ammosov, V.V. ; Andrus, A. ; Aschenauer, E.C. ; Augustyniak, W. ; Avakian, R. ; Avetissian, A. ; Avetissian, E. ; Bailey, P. ; Baturin, V. ; Baumgarten, C. ; Beckmann, M. ; Belostotski, S. ; Bernreuther, S. ; Bianchi, N. ; Blok, H.P. ; Bottcher, H. ; Borissov, A. ; Bouwhuis, M. ; Brack, J. ; Brull, A. ; Brunn, I. ; Capitani, G.P. ; Chiang, H.C. ; Ciullo, G. ; Contalbrigo, M. ; Court, G.R. ; Dalpiaz, P.F. ; De Leo, R. ; De Nardo, L. ; De Sanctis, E. ; Devitsin, E. ; Di Nezza, P. ; Duren, M. ; Ehrenfried, M. ; Elalaoui-Moulay, A. ; Elbakian, G. ; Ellinghaus, F. ; Elschenbroich, U. ; Ely, J. ; Fabbri, R. ; Fantoni, A. ; Fechtchenko, A. ; Felawka, L. ; Fox, B. ; Franz, J. ; Frullani, S. ; Garber, Y. ; Gapienko, G. ; Gapienko, V. ; Garibaldi, F. ; Garutti, E. ; Gaskell, D. ; Gavrilov, G. ; Gharibyan, V. ; Graw, G. ; Grebeniouk, O. ; Greeniaus, L.G. ; Haeberli, W. ; Hafidi, K. ; Hartig, M. ; Hasch, D. ; Heesbeen, D. ; Henoch, M. ; Hertenberger, R. ; Hesselink, W.H.A. ; Hillenbrand, A. ; Holler, Y. ; Hommez, B. ; Iarygin, G. ; Izotov, A. ; Jackson, H.E. ; Jgoun, A. ; Kaiser, R. ; Kinney, E. ; Kisselev, A. ; Konigsmann, Kay ; Kolster, H. ; Kopytin, M. ; Korotkov, V. ; Kozlov, V. ; Krauss, B. ; Krivokhijine, V.G. ; Lagamba, L. ; Lapikas, L. ; Laziev, A. ; Lenisa, P. ; Liebing, P. ; Lindemann, T. ; Lipka, K. ; Lorenzon, W. ; Makins, N.C.R. ; Marukyan, H. ; Masoli, F. ; Menden, F. ; Mexner, V. ; Meyners, N. ; Mikloukho, O. ; Miller, C.A. ; Miyachi, Y. ; Muccifora, V. ; Nagaitsev, A. ; Nappi, E. ; Naryshkin, Y. ; Nass, A. ; Nowak, W.-D. ; Oganessyan, K. ; Ohsuga, H. ; Orlandi, G. ; Potashov, S. ; Potterveld, David H. ; Raithel, M. ; Reggiani, D. ; Reimer, P.E. ; Reischl, A. ; Reolon, A.R. ; Rith, K. ; Rosner, G. ; Rostomyan, A. ; Ryckbosch, D. ; Sanjiev, I. ; Savin, Igor A. ; Scarlett, C. ; Schafer, A. ; Schill, C. ; Schnell, G. ; Schuler, K.P. ; Schwind, A. ; Seibert, J. ; Seitz, B. ; Shanidze, R. ; Shibata, T.-A. ; Shutov, V. ; Simani, M.C. ; Sinram, K. ; Stancari, M. ; Statera, M. ; Steffens, E. ; Steijger, J.J.M. ; Stewart, J. ; Stosslein, U. ; Tanaka, H. ; Taroian, S. ; Tchuiko, B. ; Terkulov, A. ; Tessarin, S. ; Thomas, E. ; Tkabladze, A. ; Trzcinski, A. ; Tytgat, M. ; Urciuoli, G.M. ; van der Nat, P.B. ; van der Steenhoven, G. ; van de Vyver, R. ; Veretennikov, D. ; Vetterli, M.C. ; Vikhrov, V. ; Vincter, M.G. ; Visser, J. ; Vogt, M. ; Volmer, J. ; Weiskopf, C. ; Wendland, J. ; Wilbert, J. ; Wise, T. ; Yen, S. ; Yoneyama, S. ; Zihlmann, B. ; Zohrabian, H. ; Zupranski, P.

Published in: Phys.Rev.
Year: 2007
Vol.: D76
Page No: 092008
Pages: 9

Abstract: The HERMES experiment has measured the transverse polarization of Lambda and Lambda-bar hyperons produced inclusively in quasireal photoproduction at a positron beam energy of 27.6 GeV. The transverse polarization of the Lambda hyperon is found to be positive while the observed Lambda-bar polarization is compatible with zero. The transverse polarization values averaged over the kinematic acceptance of HERMES are 0.078 +/- 0.006(stat) +/- 0.012(syst) and -0.025 +/- 0.015(stat) +/- 0.018(syst) for Lambda and Lambda-bar hyperons, respectively. The dependences of Lambda and Lambda-bar polarizations on the fraction $\zeta$ of the beam's light-cone momentum carried by the hyperon and on the hyperon's transverse momentum $p_T$ were investigated. The measured Lambda polarization rises linearly with $p_T$ and exhibits a different behavior for low and high values of $\zeta$, which approximately correspond to the backward and forward regions in the center-of-mass frame of the $\gamma^*N$ reaction.

Web-Page: http://link.aps.org/abstract/PRD/V76/E092008

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